A Dense Phase system conveys free flowing bulk materials using less energy, with lower material velocities, and minimal moving parts throughout the system; making it the most cost effective solution for conveying free flowing bulk materials.
Dense Phase conveying uses high pressure compressed gas (typically greater than 20psi), to convey material through a pressurized pipeline at a low velocity (less than 1000 Ft./Min.). In a Dense Phase system the material is conveyed below its minimum pick up velocity in the form of a fluid plug. The material being conveyed as a fluid plug creates enough resistance to allow pressure to build. The sizing of both the pressure vessel and convey pipeline is critical in achieving optimal dense phase conveying performance.
Virtually any dry, free flowing, powder like materials are candidates for dense phase conveying, but considering the main principle of dense phase pneumatic conveying (low material velocity); makes it a prime candidate for conveying abrasive materials. Not only does a dense phase system convey material at low velocities (up to 10 times slower than dilute phase applications), but it will typically have fewer moving parts than other forms of conveying (a typical JDB system will only have one moving part in the entire system; the Dense Flow Cone Valve). The low material velocities, and minimal moving parts that make up a dense phase pneumatic conveying system translates into a conveying system with minimal maintenance, less downtime, less wear and tear on pipeline components, and greater efficiency than other forms of bulk material conveying.
Dense Phase System Layout and Sequence of Operations:
- Once the pressure vessel is full a valve(s) closes and seals the pressure vessel.
- Note: the pressure vessel inlet is sealed but the convey pipeline discharge is not.
- Compressed air is introduced into the system.
- The compressed air being introduced in to the system will seek the path of least resistance (out the end of the convey pipeline discharge).
- As air is being introduced and trying to escape out the end of the convey pipeline, the material will be forced out of the pressure vessel and into the convey pipeline (think of squeezing a tube of toothpaste). As the material is forced from a large diameter pressure vessel down to the smaller diameter convey pipeline the resistance of the material forms a fluid plug, where compressed air is forcing the material through the convey line towards the discharge.
- As the material is forced out of the pressure vessel through the pipeline the materials velocity will gradually increase, and as the velocities increase, air will begin slipping past some of the material. As the air begins slipping past the material air pockets will form behind several smaller slugs of material. If you were to view the material moving through a transparent pipeline it would look like sand dunes moving.
- When the material begins to exit the convey pipeline and reach its final destination (silo, bin, etc.) the resistance from the materials fluid plug is no longer present, and the pressure within the system will decrease. This decrease in pressure signals that the material has reached its destination and the sequence can start over.